Use of 3-methoxy-pregnenolone for the preparation of a drug for treating depressive disorders and long-term neurological diseases

ABSTRACT

The invention relates to the therapeutic use of pregnenolone derivatives for treating depressive disorders and long-term neurological diseases.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of, and claims priority from, U.S. Ser. No. 10/542,495 filed Jul. 15, 2005, which claims priority under 35 U.S.C. 371 from PCT/FR04/00086 filed on Jan. 16, 2004, which claims priority from French application No. 0300507 filed on Jan. 17, 2003. The content of each of the prior applications are incorporated herein by reference.

TECHNICAL FIELD

The invention involves an innovative use of neurosteroid derivatives, notably pregnenolone and pregnenolone derivatives, to treat nervous system lesions and certain neurodegenerative diseases, notably linked to the ability of the aforementioned neurosteroid derivatives to stabilize and/or increase the polymerization of neuronal microtubules. The invention further relates to the therapeutic use of particular pregnenolone derivatives for treating depressive disorders.

BACKGROUND ART

Mood disorders include major and bipolar depression and are common, chronic and life threatening illnesses in Western society (Maris, Lancet 2002). Major depression affects 8-12% of the population (Andrade et al., Int. J. Meth. Psychiatr. Res. 2003) and 15% of suicides are committed by depressives in the USA (Manji et al., Nat. Med. 2001). Major depression is traditionally associated with low levels of the central nervous system (CNS) monoamines (i.e. serotonin [5-HT], dopamine [DA], norepinephrine [NE]). Antidepressant drugs target monoaminergic function by preventing their reuptake presynaptically or blocking their metabolism. Although antidepressants seem to exert their initial effect by immediately increasing monoaminergic levels intrasynaptically (Malagie et al., Eur. J. Pharmacol. 1995; Romero et al., J. Neurochem. 1996) their clinical efficacy occurs only after chronic administration (Blier and de Montigny, TiPS 1994). These findings lead the scientific community to the novel hypothesis that enhanced monoaminergic neurotransmission per se is not sufficient to explain the clinical actions of antidepressant drugs (Warner-Schmidt and Duman, Hippocampus 2006). Recently, magnetic resonance studies showed volume loss and structural abnormality in the hippocampus of depressed individuals (Campbell and Macqueen, J. Psychiatry Neurosci. 2004). Stress and major depression appear to be closely related and pre-clinical studies employing stress as predisposing factor to depression suggest that the hippocampal structural alterations observed in depressed patients may result from dendritic atrophy, neuriteal alterations, structural glial changes and neurogenesis decrease (Warner-Schmidt and Duman, Hippocampus. 2006). Importantly, chronic treatment with antidepressant drugs seems to prevent stress-induced neuronal plasticity alterations in rodents (Warner-Schmidt and Duman, Hippocampus 2006). Consequently, the pathogenesis of depression may also involve stress-induced structural alterations in specific brain regions with the same features of dendrite alterations and impaired neurogenesis. The dynamics of the cytoskeletal microtubular system are fundamental for the formation and maintenance of synaptic connectivity including remodeling and extension of neurites (Mitchison and Kirschner, Neuron 1988) and dendrites (Vaillant et al., Neuron 2002). Microtubules are formed by the polymerization of the tubulin α/β heterodimers and in higher vertebrates three α-tubulins (α1, α2, and α4) and five β-tubulins (βI, βII, βIII, βIVa and βIVb) isotypes are specifically expressed in the brain (Luduena, Int. Rev. Cytol. 1998). Microtubules specifically interact with different proteins named microtubule-associated proteins (MAPs), between them the microtubule-associated protein 2 (MAP2) isoforms and TAU represent the major components of the proteins interacting with neuronal microtubules. They are present in all the extensions which constitute the dendritic arborization of a neuron, such neuronal branches are a key factor for the establishment of synaptic connections (Matus, Microtubules 1994; Sanchez et al., Prog. Neurobiol 2000). MAP2 proteins are necessary for the formation of dendrites since suppression of MAP2 synthesis caused either neuritic growth to stop in neurons in culture (Caceres et al., Neuron 1992) or dendritic growth to stop in MAP2 knockout mice (Harada et al., J. Cell. Biol. 2002). However, the synthesis of MAP2 proteins is not in and of itself sufficient to induce this dendritic growth process. Certain steroids such as estradiol or progesterone can induce an increase in MAP2 synthesis without inducing significant morphological changes (Reyna-Neyra et al., Brain Res. 2002). Recent data showed that experimental models of stress and depression such as restraint stress (Bianchi et al., Synapse 2003), forced swimming test (Bianchi et al., Curr. Drug Targets CNS Neurol. Disord. 2005) and social isolation (Bianchi et al., EJN 2006) induce abnormal microtubule stabilization and dendrite retraction in rat hippocampus. Additionally, different stressors and administration of glucocorticoids can change the expression of different MAPs including MAP-2, MAP-1A and TAU in rat hippocampus (for an extensive review see Bianchi et al., Curr. Drug Targets CNS Neurol. Disord. 2005). Finally, antidepressant drugs can affect MAP2 function and in turn the dynamics of the microtubular system. Indeed, both 5-HT and NE reuptake inhibitors differentially increased MAP2 phosphorylation and decreased microtubule assembly (i.e. increased microtubule dynamics) in rat cerebral cortex (Perez et al., Neuropsychopharmacology 1991; Miyamoto et al., Eur. J. Pharmacol. 1997) and in neuroblastoma cells (Donati and Rasenick, Neuropsychopharmacology 2005). Taken all together, these findings lead to the original hypothesis that the pathogenesis and treatment of depression may include changes in microtubule dynamics (Bianchi et al., Curr. Drug Targets. CNS Neurol. Disord. 2005).

Neurodegenerative diseases and CNS lesion such as spinal cord and brain injury are widespread conditions with devastating effects on the life of the patients and their close relatives. As an example, about 450,000 people in the USA live with spinal cord injury (1 in 670) and only 5% of patients with complete injury recover locomotion. Despite many research efforts in the field, effective molecules for the treatment of neurodegenerative diseases and CNS lesions are still not available. Interestingly, neurodegenerative diseases and CNS lesions share many pathogenetical similarities including deterioration of neuronal cytoskeleton. This deterioration can be the consequence but also the cause of damage to the affected cells. Growing evidence suggest that the cytoskeletal degradation observed after spinal cord injury (Zhang et al., J Neuropathol Exp Neurol 2000) results from increased extracellular glutamate which in turn increases intracellular Ca⁺⁺ by activation of ion channels. Thus, the accumulation of intracellular Ca⁺⁺ (i.e. Ca⁺⁺ overload) can activate the protease calpain which induces proteolysis of MAP2 and TAU leading to abnormal microtubule depolymerization. The use of a calpain inhibitor (Schumacher et al., J Neurochem 2000) and the salting-out of glutamate (Springer et al., J Neurochem 1997) decrease the consequences of spinal cord injury in rodents by partially preserving the cytoskeleton.

Importantly, the MAP2/TAU loss and microtubule depolymerization observed in spinal cord and brain injury can be directly responsible for the dysfunction of certain neurons and can result in their death. Moreover, such cytoskeletal deterioration can affect the number and the length of the neuritic extensions of the remaining neuronal cells and, as a consequence, decreases their effectiveness. Consistently, treatment with nerve growth factor (NGF), which prevents dendritic atrophy, enables better functional recovery after a lesion of the cerebral cortex in the rat (Kolb et al., Neuroscience 1997).

The existence of stem cells in certain regions of the central nervous system is well established today. Lesions stimulate the proliferation of these cells. However, these cells must migrate and differentiate. Differentiation implies, at a fundamental level, the development of the cytoskeleton.

It has been shown recently that, after cerebral ischemia, stem cells could differentiate into neurons and become integrated into the existing neuronal circuits (Nakatomi et al., Cell 2002). Similarly, it is well established that antidepressant drugs stimulate neurogenesis in the sub-granular zone of adult hippocampus and newborn cell migrate to the granule cell layer to become mature neurons extending dendrites and neurites (Warner-Schmidt and Duman, Hippocampus 2006).

The stimulation of dendrite and/or neurite growth (neuronal branching outgrowth) in these stem cells, and in already existing mature neurons, by molecules that improve tubulin polymerization and microtubule function could increase and or recover the number of functional synaptic connections.

Pregnenolone (PREG) binds to MAP2 and has the extremely important and original property of reinforcing the activity of this protein, namely its role in the activation of the tubulin polymerization process and the establishment of microtubular structures of greater function (Murakami et al., Proc Natl Acad Sci USA 2000).

In spite of much research, at present no specific targets other than MAPs have been identified for PREG.

MAP2 protein is found primarily in neurons. It is therefore probable that MAP2 binding molecules mainly target the cells of the nervous system, without having a notable action on other cellular types in which the concentration of MAP2 is very low.

Studies that demonstrate an in vivo effect by PREG are very few but they suggest a beneficial role for this steroid. It was shown that PREG administration decreased the reaction (formation of gliotic tissue (i.e. accumulation of astrocytes)) following a penetrating lesion in rat cerebral cortex and hippocampus (Garcia-Estrada et al., Int J Devl Neuroscience 1999). Additionally, PREG administration reverses the age-dependent accumulation of glial fibrillary acidic protein within astrocytes of specific regions of the rat brain (Legrand and Alonso, Brain Res. 1998). PREG also contributed to improved functional recovery after a medullary (spinal cord) trauma (Guth et al., Proc Natl Acad Sci USA 1994). Furthermore, PREG was showed to protect against toxicity induced by glutamate and the protein beta amyloid in hippocampal cells line (HT-22) cultures (Gursoy et al., Neurochem Res. 2001).

On the other hand, decreased levels of PREG have been reported in the cerebrospinal fluid of depressed patients (George et al., Biol. Psych. 1994). Furthermore, a first clinical investigation on the effects of PREG in healthy volunteers revealed a general tendency of reduced subjective depression ratings (Meieran et al., Psychoneuroendocrinology 2004). Moreover, antidepressant drugs increased PREG levels in rat hippocampus (Serra et al., Psychopharmacology 2001), while models of depression such as social isolation decreased it (Serra et al., J. Neurochem. 2000). Thus, PREG has been shown as having some beneficial effect in the CNS, both in case of traumatic lesion and in case of depressive disorders.

PREG is a metabolite of cholesterol and the precursor of all steroid hormones. The synthesis of these hormones implies the conversion of the PREG Δ5-3β-OH structure to Δ4-3-ketone derivatives (implemented by an enzyme called 3βHSD). The Applicant blocked the Δ5-3β-OH structure to prevent this metabolic conversion and also to prevent the formation of the ester sulfate of PREG, a molecule that can be detrimental at high concentrations. Thus, the Applicant has revealed a compound, 3-methoxy-pregnenolone (3β-methoxy-pregna-5-ene-20-one, abbreviated as 3-methoxy-PREG), which possesses these properties and which, moreover, is at least as active as PREG in promoting microtubule polymerization and function. It was verified by mass spectrometry coupled with gas chromatography that 3-methoxy-PREG is not converted into PREG.

DESCRIPTION OF THE INVENTION

The Applicant considers as well that the invention is related to 3-methoxy-PREG, but also to all the steroid and steroid-like molecules derived from or mimicking PREG, and in particular molecules derived from PREG, that contain a 3-methoxy function or present a 3β function that can be converted into 3-methyl-ether. These molecules are incapable then of being converted into metabolites endowed with progestative (progesterone is a direct metabolite of PREG and, in addition to its hormonal activity, it is an in vitro PREG antagonist for the polymerization of microtubules), androgenic, estrogenic, glucocorticoid and mineralcorticoid activity. Also, they cannot be converted into ester sulfates which, such as the sulfate of PREG, can lead to undesired (neurotoxic) side effects.

Within the scope of this invention, the Applicant has revealed the fact that 3-methoxy-PREG, or other molecules according to the invention, can play a major role in the polymerization and/or stabilization of microtubules, and presents quite remarkable activities for the treatment of pathologies related to the nervous system.

By “pathologies related to the nervous system” it is meant pathologies related to the central or peripheral nervous system, particularly those pathologies in which neurocellular microtubules are affected.

3-methoxy-PREG presents the following formula:

Thus, the invention relates to the use of 3-methoxy-PREG or any molecule derived from pregnenolone or from others 3β-hydroxylated steroids/sterols (or non steroidal derivatives), incapable of being converted into sulfate esters and/or incapable to be converted by oxidation to hormonally active molecules, for the preparation of a drug intended to stimulate the polymerization, stabilization and function of neuronal microtubules to treat pathologies related to the nervous system particularly acute or chronic lesions or a degenerative disease or depressive disorder with the aforementioned molecule presenting general formula I:

in which:

represents

R1=—CO—; —CH(OH)— or —CH(O—COCH₃)—

R2=H or CHCl₂,

R3=H or CH₃, or

R2 and R3 together form a ring:

the invention relates to the use of 3-methoxy-PREG or a molecule derived from pregnenolone that contains a 3-methoxy function and is incapable of being converted into a metabolite or ester sulfate of pregnenolone, for the preparation of a drug intended to stimulate the polymerization and/or the stabilization of microtubules to treat an acute or chronic lesion or a degenerative disease or a depressive state of the nervous system with the aforementioned molecule presenting general formula I:

in which:

represents

R1=—CO—; —CH(OH)— or —CH(O—COCH₃)—

R2=H or CHCl₂,

R3=H or CH₃, or

R2 and R3 together form a ring:

In a preferred embodiment, the aforementioned molecule is 3-methoxy-PREG (3β-methoxy-pregna-5-ene-20-one).

In another embodiment, the aforementioned molecule is 3β-methoxy-pregna-5-ene-20-one-17-α-dichloromethyl.

In another embodiment, the aforementioned molecule is 3β-methoxy-5α-pregnane-20-one.

In another embodiment, the aforementioned molecule is 3β-methoxy-5α-pregnane-20β-ol.

In another embodiment, the aforementioned molecule is 3β-methoxy-PREG-16α-methyl.

In another embodiment, the aforementioned molecule is 3β-methoxy-PREG-16β-methyl.

In another embodiment, the aforementioned molecule is 3β-methoxy-pregna-5,14-diene-20-one.

In another embodiment, the aforementioned molecule is 3β-methoxy-PREG-16α,17α-epoxy.

In another embodiment, the aforementioned molecule is 3β-methoxy-PREG-16α,17α-methylene.

In another embodiment, the aforementioned molecule is 3β-methoxy-pregna-5-ene-3β,20β-diol-20-acetate.

In another embodiment, the aforementioned molecule is 3β-methoxy-5α-pregnane-20-one-16α-methyl.

3-methoxy-PREG can, within the scope of the present invention, be used to prepare a useful drug to treat other syndromes such as mental slowdown and loss of concentration, pain, including acute pain, post-operative pain, chronic pain, nociceptive pain, neuropathic pain, psychogenic pain syndromes, pain associated with peripheral neuropathies, certain psychiatric states (notably depressive disorders and schizophrenia), dissociative episodes including dissociative amnesia, dissociative fugue and dissociative identity disorder, and other neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, tauopathies, diseases related to prions, amyotrophic lateral sclerosis (ALS), and multiple sclerosis.

In a general way, 3-methoxy-PREG or the molecules derived according to the invention are used to treat any disease in which increased (neuronal) microtubule polymerization and/or stabilization and/or function is sought or is beneficial.

In a preferred embodiment according to the invention, the aforementioned disease is selected from the group comprising Alzheimer's disease, Parkinson's disease, Huntington's disease, tauopathies, age-induced memory loss, age-related dementia, memory loss induced by the taking of substances, a traumatic brain or spinal cord lesion, in particular a traumatic brain or spinal cord lesion, a cerebral lesion, a lesion of the spinal cord, in particular medullary (spinal cord) compression, ischemia, pain, notably neuritic pain, nerve degeneration, and multiple sclerosis.

In another preferred embodiment, 3-methoxy-PREG or the molecule derived of formula I according to the invention is used to treat depressive disorders.

Depression is a mood disorder and can be defined as a mental state characterized by a pessimistic sense of inadequacy and a despondent lack of activity which needs medical treatment due to the high risk of suicide.

The two main types of mood disorders are major (unipolar) depression and bipolar disorder. Major depression is diagnosed following standard clinical criteria such as those recommended by the American Psychiatric Association in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). Accordingly, individuals are considered to have an episode of major depression when depressed mood, loss of interest or diminished sense of pleasure have been clearly evident for at least two weeks. Additionally, they have to show five of more of other features nearly every day during the same two week span. These features include large increase or decrease in appetite, insomnia or excessive sleeping, restlessness or slowness of movement, fatigue or loss of energy, feelings of worthlessness or excessive or inappropriate guilt, diminished concentration and decisiveness, suicidal ideation or suicidal attempts.

Episodes may be isolated or recurrent and categorized as mild, moderate or severe based on the intensity of depressive symptoms. In DSM-IV, depression is classified under codes 296.20 to 296.26 for Major depressive disorder, single episode; 296.30 to 296.36 for Major depressive disorder, recurrent; 300.4 for Dysthymic disorder; and 311 for Depressive disorder Not Otherwise Specified.

Common subtypes of major depression include atypical depression, melancholic depression, psychotic depression and geriatric depression. Other subtypes include dysthymia, postpartum depression, post stroke depression, and subcortical ischemic depression.

Atypical depression is characterized by mood reactivity (paradoxical anhedonia) and positivity, significant weight gain or increased appetite, excessive sleep or somnolence (hypersomnia), leaden paralysis, or significant social impairment as a consequence of hypersensitivity to perceived interpersonal rejection. Contrary to its name, atypical depression is between the most common forms of depression.

Melancholic depression is characterized by a loss of pleasure in most or all activities, a failure of reactivity to pleasurable stimuli, severe depressed mood and excessive guilt, a worsening of symptoms in the morning hours, early morning waking, psychomotor retardation, excessive weight loss and decreased appetite.

Psychotic depression is characterized by psychotic (schizophrenic-like) features. These features include hallucinations or delusions that are either mood-congruent (content coincident with depressive themes) or non-mood-congruent (content not coincident with depressive themes).

Finally, geriatric depression affects about 5% to 15% of community-dwelling older adults (i.e. adults aged 65 years or more) and is characterized by impairments in cognition (a syndrome sometimes referred as pseudodementia), by psychomotor agitation or retardation, and by high rates of suicide. Clinical major depression can present a combination of these subtypes. For instance someone may experience loss of pleasure in activities as seen in melancholic depression in addition to over-eating and weight gain common to atypical depression.

In a preferred embodiment, 3-methoxy-PREG or the molecules derived of formula I according to the invention, used to treat depressive disorders, are used for treating major depression, dysthymia, postpartum depression, post stroke depression, and subcortical ischemic depression. Preferably, when major depression is treated, it is selected from the group consisting of atypical depression, melancholic depression, psychotic depression and geriatric depression.

In a preferred embodiment, and notably to treat diseases related to a central nervous system disturbance, the aforementioned drug also comprises an excipient or a compound that makes it possible to formulate the aforementioned 3-methoxy-PREG such that it crosses the blood-brain barrier better. Such an excipient or compound can also make possible a faster or more long-lasting crossing of the aforesaid blood-brain barrier.

Such an excipient or compound can be a peptide, such as the peptides described in application WO 00/32236, or 2-pyrrolidone.

The pharmaceutical compositions used in the invention can be administered by any route of administration including, but without being limited to, oral, intravenous, intramuscular, intraarterial, intramedullary, intratechal, intraventricular, transdermal, subcutaneous, intraperitoneal, intranasal, enteral, topical, sublingual, vaginal and rectal.

A continuous or long-term treatment conducted directly via the cerebrospinal fluid using a pump implanted in the subarachnoid space in the brain or spinal cord can be envisaged. Such an implant could contain a concentrated solution of 3-methoxy-PREG (for example of isopropyl-beta-cyclodextrin diluted with artificial cerebrospinal fluid).

Moreover, 3-methoxy-PREG can be administered with other compounds that contain biologically active agents (for example tensioactives, excipients, transporters, thinners and/or pharmaceutically acceptable vehicles). These compounds are well-known to those skilled in the art. Details on these chemicals can be found in the latest edition of Remington's Pharmaceutical Sciences (Maack Publishing Co., Easton, Pa.).

In the pharmaceutical compositions provided by the present invention for oral, sublingual, subcutaneous, intramuscular, intravenous, transdermal, local, vaginal or rectal administration, the active ingredient (3-methoxy-PREG or a derived molecule) can be administered in unit dose formulations or in mixtures with traditional pharmaceutical media, applicable to animals or humans. Suitable unit dose administration formulations include oral route formulations such as tablets, coated tablets, pills, capsules and soft gelatin capsules, oral powders, granules, solutions and suspensions, sublingual and buccal administration formulations, subcutaneous, intramuscular, intravenous, intranasal, and intraocular administration formulations, and vaginal or rectal administration formulations.

Pharmaceutical compositions can also contain preservatives, solubilizing agents, stabilizers, wetting agents, emulsifiers, sweeteners, dyes, flavoring, salts intended to modify osmotic pressure, buffers, taste correctors, and antioxidants. They can also contain other therapeutically active substances.

Thus, pharmaceutical compositions according to the invention can also contain other steroids known to exert pro-cognitive effects. Additionally, neuroprotective and neurostimulant agents can also be included in the pharmaceutical composition, notably compounds which increase neuronal regeneration. Such agents can be selected in particular from among the neuronal growth factors such as fibroblast growth factors (FGFs), acidic or basic, FGF-3, FGF-4, FGF-6, or keratinocyte growth factor (KGF). The addition of a neuroprotective agent can be envisaged, such as nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), neurotrophin 3 or 4, TGF-beta.l, interleukins, or insulin-like growth factors (IGFs). Finally, the addition of peptides known to bind other microtubular components such as the activity-dependent neuroprotective protein (ADNP) and the ADNP-related peptide NAP, which bind the neuronal βIII-tubulin, can be also considered due to their promoting effect on microtubule polymerization and function and their neuroprotective properties (Gozes et al., CNS Drug Rev. 2005).

Any other types of therapeutic antioxidant or neuroprotective agents can be used, notably glutamate inhibitors.

When a solid composition in tablet form is prepared, the principal active ingredient is mixed with a pharmaceutical vehicle such as gelatin, starch, lactose, stearic acid or magnesium stearate, talc, gum arabic or analogues. The tablets can be coated with saccharose or other suitable materials or even be treated so as to have a prolonged or delayed activity and to release continuously a predetermined quantity of the active ingredient.

A capsule preparation is obtained by mixing the active ingredient with a thinner and pouring the mixture obtained into soft or hard capsules, with excipients such as vegetable oils, waxes, fats, semi-solid or liquid polyols, etc.

A preparation in syrup or elixir form can contain the active ingredient together with a sweetener, an antiseptic, as well as an agent giving taste and a suitable dye. Excipients can be used such as water, polyols, saccharose, invert sugar, glucose, etc.

Powders or water-dispersible granules can contain the active ingredient in a mixture with dispersing agents, wetting agents, and suspending agents, together with taste correctors and sweeteners.

Suppositories, which are prepared with binders that melt at rectal temperatures, for example cocoa butter or semi-solid or liquid polyols such as polyethylene glycols, waxes, natural or hydrogenated oils, fats, etc., can be used for vaginal or rectal administration.

For parenteral, intranasal, or intraocular administration, aqueous suspensions, isotonic saline solutions, or sterile, injectable solutions that contain pharmacologically compatible dispersing agents and/or wetting agents can be used. As an excipient, water, alcohols, polyols, glycerol, vegetable oils, etc., can be used.

The active ingredient can also be formulated in the form of microcapsules, possibly with one or more additive supports.

For the treatment of pain, topical application is the preferred route of administration. Here, the compositions according to the invention can be presented in the form of a gel, a paste, an ointment, a cream, a lotion, an aqueous or aqueous-alcohol liquid suspension, an oily solution, a dispersion of the lotion or serum type, an anhydrous or lipophilic gel, an emulsion with a liquid or semi-solid milk-type consistency obtained by dispersing a fatty phase in an aqueous phase or vice versa, suspensions or emulsions of a soft or semi-solid cream- or gel-type consistency, or alternatively microemulsions, microcapsules, microparticles, or vesicular dispersions of the ionic and/or nonionic type. These compositions are prepared according to standard methods.

Moreover, a tensioactive can be included in the composition in order to enable deeper penetration by 3-methoxy-PREG.

Among the ingredients envisaged, the invention comprises agents enabling an increase in penetration selected, for example, from the group comprising mineral oil, ethanol, triacetin, glycerin and propylene glycol; cohesion agents are selected, for example, from the group comprising polyisobutylene, polyvinyl acetate, polyvinyl alcohol, and thickening agents.

Thus, in a preferred embodiment according to the invention, the aforementioned drug is presented in an injectable form.

In another preferred embodiment according to the invention, the aforementioned drug is presented in a form allowing oral administration.

Preferably, the aforementioned drug comprises an effective quantity of 3-methoxy-PREG, in particular ranging between 25 and 2500 mg, preferably between 25 and 250 mg, and by the parenteral route.

The aforementioned drug comprises preferentially an effective quantity of 3-methoxy-PREG or any molecule derived from pregnenolone or from 3β-hydroxylated steroids/sterols, incapable of being converted into sulfate esters and/or incapable to be converted by oxidation to hormonally active molecules, preferably 3-methoxy-PREG or a molecule derived from pregnenolone that presents a 3-methoxy function, such that the quantity administered to the patient is comprised between 0.1 and 100 mg/kg body weight, preferably between 1 and 100 mg/kg body weight, or between 0.1 and 10 mg/kg body weight.

An effective quantity of 3-methoxy-PREG is a quantity which allows, within the meaning of the present invention, the stabilization and/or polymerization of microtubules after administration to the host. Thus, the administration of an effective quantity of 3-methoxy-PREG results in the retardation, the improvement or the elimination of the disease. The quantity of 3-methoxy-PREG administered to the host will vary as a function of factors which include the height, age, weight, general health, sex, and diet of the host, the time of the administration, and the duration and characteristics of the disease associated with microtubule depolymerization/destabilization. The adjustment of dosages is well-known to those skilled in the art.

Thus, the invention relates to a therapeutic use of 3-methoxy-PREG. Thus, the invention relates to this compound as a drug.

A pharmaceutical composition comprising as an active ingredient 3-methoxy-PREG or any molecule derived from pregnenolone or from others 3β-hydroxylated steroids/sterols, incapable of being converted into sulfate esters and/or incapable to be converted by oxidation to hormonally active molecules, preferably 3-methoxy-PREG or a compound derived from pregnenolone having a 3-methoxy function of general formula I, and a pharmaceutically acceptable excipient, is also an object of the invention.

The Applicant has revealed the activity of 3-methoxy-PREG which stabilizes and/or induces microtubule polymerization in a cell.

Thus, in a more general way, the invention relates to a method for increasing the stabilization and/or inducing the polymerization of the microtubules in a cell, comprising the step of exposing the aforementioned cell to the presence of 3-methoxy-PREG at a concentration from approximately 0.1 to 100 μM or 0.5 to 100 μM, preferably 0.1 to 50 μM or 0.5 to 50 μM. Microtubule polymerization can be analyzed by immunolabeling the MAP2 protein associated with these microtubules. Preferably, this method is implemented in vitro, but can be implemented in vivo, or ex vivo (on cells isolated from a patient, treated in vitro and re-injected) in certain cases.

The invention also relates to a method for increasing the growth of neurites in a cell, comprising the step of exposing the aforementioned cell to the presence of 3-methoxy-PREG at a concentration from approximately 0.5 to 50 μM. This method is also implemented in vitro by preference, without excluding other modes of implementation if necessary.

The invention also relates to a method for promoting neurites branching in neuronal cells, comprising the step of exposing the aforementioned cell to the presence of 3-methoxy-PREG at a concentration from approximately 0.1 to 50 μM. This method is also implemented in vitro by preference, without excluding other ways of implementation if necessary.

The invention has also as an aim a method for reducing the depolymerization of microtubules and/or the retraction of neurites in a cell, comprising the step of exposing the aforementioned cell to the presence of 3-methoxy-PREG at a concentration from approximately 0.5 to 50 μM. This method is implemented in vitro also by preference, without excluding other modes of implementation if necessary.

The invention has also as an aim a method for reducing the depolymerization of microtubules and/or recovering the extension of neurites in a cell, comprising the step of exposing the aforementioned cell to the presence of 3-methoxy-PREG at a concentration from approximately 0.1 to 50 μM. This method is implemented in vitro also by preference, without excluding other ways of implementation if necessary.

The invention also relates to a method for the treatment and/or the prevention of a disease induced or accompanied by the depolymerization of microtubules in a patient, comprising the step of the administration of an effective quantity of 3-methoxy-PREG to the aforementioned patient. As mentioned before, the invention is related to 3-methoxy-PREG or any molecule derived from pregnenolone or from 3β-hydroxylated steroids/sterols, incapable of being converted into sulfate esters and/or incapable to be converted by oxidation to hormonally active molecules. Preferably, the invention relates to 3-methoxy-PREG, but also to all the molecules derived from pregnenolone that contain a 3-methoxy function or present a 3′ function that can be converted into 3-methyl-ether and is incapable of being converted into a metabolite or ester sulfate of pregnenolone, said molecule being of formula I.

In a particular embodiment, the invention thus relates to a method for the treatment and/or the prevention of a disease induced or accompanied by the depolymerization of microtubules in a patient, comprising the step of the administration to said patient of an effective quantity of 3-methoxy-PREG or any molecule derived from pregnenolone or from others 3β-hydroxylated steroids/sterols, incapable of being converted into sulfate esters and/or incapable to be converted by oxidation to hormonally active molecules, preferably of 3-methoxy-PREG or a molecule derived from pregnenolone that contains a 3-methoxy function and is incapable of being converted into a metabolite or ester sulfate of pregnenolone of formula I, wherein said disease is a depressive disorder. In a preferred embodiment, said depressive disorder is selected from the group consisting of major depression, dysthymia, postpartum depression, post stroke depression, and subcortical ischemic depression. More particularly, when major depression is treated, major depression is advantageously selected from the group consisting of atypical depression, melancholic depression and psychotic depression.

In such methods according to the invention, any molecule of formula I, any excipient, any administration route, or any dosage mentioned above may be used.

The invention also relates to a method for the treatment and/or the prevention of a neurodegenerative disease or lesion in a patient, comprising the step of the administration of an effective quantity of 3-methoxy-PREG to the aforementioned patient.

A method to treat a patient after medullary compression or trauma, comprising the step of the administration of an effective quantity of 3-methoxy-PREG to the aforementioned patient, is also an object of the invention.

Finally, a method to treat a patient after spinal cord or brain compression or trauma, comprising the step of the administration of an effective quantity of 3-methoxy-PREG to the aforementioned patient, is also an object of the invention.

DESCRIPTION OF FIGURES

FIG. 1: Kinetics of microtubule polymerization in vitro: effects of PREG (pregnenolone) and molecule 43B (3-methoxy-PREG) both at a concentration of 40 μM. Purified MAP2 and tubulin are mixed in the presence of GTP at 4° C. in a spectrophotometer cuvette. Polymerization is induced by heating at 37° C. and is followed by the increase in optical density (OD) which indicates the quantity of polymers formed. Lag time is decreased in the presence of PREG and molecule 43B, whereas the polymerization rate and the quantity of microtubules clearly increase compared to the control kinetics in the presence of solvent alone.

FIG. 2: Effect of PREG and 3-methoxy-PREG (43B) on the average length of neurites in PC12 cells. PC12 cells were cultured for 3 days in the presence of NGF (10 ng/ml) with or without (control) the addition of PREG or 43B molecules (30 μM). Each molecule was tested in three culture wells. Measurements were taken for 200 cells per well using Scion Image software.

FIG. 3: Dose-response relationship of molecule 43B on the average length of neurites (neurites) in PC12 cells. PC12 cells were cultured in the presence of NGF (10 ng/ml) and increasing concentrations of 3-methoxy-PREG (43B). Neurite (neurite) length was measured for 200 cells per well after 2, 5, and 8 days of culture.

FIG. 4: Immunolabeling of microtubule-associated MAP2 in PC12 cells treated with PREG or 3-methoxy-PREG. PC12 cells were cultured in the presence of NGF (10 ng/ml) and PREG or 3-methoxy-PREG (20 μM). They were fixed and exposed to anti-MAP2 antibodies that reveal microtubule-associated MAP2 exclusively.

FIG. 5: Retraction of neurites (neurites) induced by nocodazole. After 7 days of culture in the presence of NGF (10 ng/ml), the cells were pretreated for one hour with PREG (30 μM) or 43B (30 μM), then exposed to nocodazole for 15 minutes (white columns: DMSO solvent alone; gray columns: nocodazole).

FIG. 6: Toxicity of okadaic acid. Steroid protection. Human neuroblastoma HS-SY5Y cells were cultured for 24 hours in the presence of okadaic acid only or associated with increasing concentrations of PREG or 3-methoxy-PREG. Cell death was indicated by the release of lactate dehydrogenase (LDH) in the culture medium.

FIG. 7: Effect of molecule 43B on locomotor recovery following medullary (spinal cord) compression in rats. Animal locomotion was evaluated in a blind format during the 1-28 day post-operative period using the BBB score which evaluates the degree of paralysis (higher values correspond to better recovery). Statistical significance: * indicates p<0.001; ** indicates p<0.0001.

FIG. 8: Effect of molecule 43B on the motor incoordination of transgenic mice expressing the longest isoform of human tau protein in their neurons. Motor incoordination was evaluated in a blind format during 12 weeks following subcutaneous insertion of an implant that was empty or contained either PREG or 3-methoxy-PREG (43B). The maximum speed of rotation of the RotaRod drum before the rat falls is a measurement of motor coordination (higher values correspond to a better treatment effect).

FIG. 9: Kinetics of the appearance of 3-methoxy-PREG (43B) in rat brain and spinal cord following subcutaneous injection of 43B (12 mg/kg) in a sesame oil solution.

FIG. 10: Test of progesterone receptor agonist activity.

FIG. 11: Test of progesterone receptor antagonist activity

FIG. 12: A single administration of pregnenolone (PREG) and 3-methoxy-PREG (43B) (10 mg/kg subcutaneously) increased microtubule dynamics in rat hippocampus, but a single administration of the antidepressant fluoxetine (FLX) (10 mg/kg subcutaneously) did not. (A) PREG and 43B induced a significant increase in Tyr/Glu-Tub ratio (index of microtubule dynamics), but FLX did not. (B) PREG and 43B induced a significant decrease in Acet-Tub (marker of stable microtubules), while FLX showed a tendency to increase it. Mean±SEM, n=6 per group. **p<0.01, *p<0.5 vs sesame oil.

FIG. 13: Antidepressant effects of pregnenolone (PREG) and 3-methoxy-PREG (43B) compared to those of the antidepressant drugs fluoxetine (FLX) and desipramine (DMI) in rats. (A) 3-methoxy-PREG (43B) decreased rat immobility in the FST showing antidepressant activity. Results are expressed as mean±SEM (n=6-14). One-way ANOVA: Treatment (F5, 46: 4.30 P<0.01). ***P<0.001, *P<0.05 vs. water and sesame oil (Fisher LSD test). (B) PREG and 3-methoxy-PREG (43B) increased rat swimming in the FST showing a fluoxetine-like (serotonin re-uptake inhibitor) profile. Results are expressed as mean±SEM (n=6-14). One-way ANOVA: Treatment (F5, 46: 3.57 P<0.01). **P<0.01, *P<0.05 vs. water and sesame oil (Fisher LSD test) (C) 3-methoxy-PREG (43B) did not affect rat climbing in the FST showing. One-way ANOVA: Treatment (F5, 46: 3.57 P<0.01). **P<0.01, *P<0.05 vs. water and sesame oil (Fisher LSD test).

FIG. 14: 3-methoxy-PREG (43B) enhanced retention of recognition memory in naïve animals and recovered recognition memory deficits in social isolated rats. (A) Sesame Oil treated rats cannot discriminate between the novel and the familiar object following a 4 h inter trial interval (ITI) time. In contrast, 43B (10 mg/kg subcutaneously) treated rats retain the ability to discriminate between the novel and the familiar object. Mean±SEM, n=11-12 per group. ***p<0.001 vs sesame oil (T-test). (B) Isolated animals treated with sesame oil cannot discriminate between the novel and the familiar object following 1 ITI, while grouped (control) rats clearly discriminate. In contrast, isolated animals receiving a single injection of 43B (10 mg/kg subcutaneously) 1 h before performing the task, recovered such recognition memory deficits. Mean±SEM, n=7 per group. ***p<0.001 vs grouped sesame oil (T-test).

The examples which follow are intended to illustrate the invention.

EXAMPLES Example 1 Synthesis of 3-methoxy-PREG (43B)

10 g (52 mmol) of p-toluenesulfonyl chloride is added to a solution of 5 g (15.8 mmol) of pregnenolone in 30 ml of pyridine. The mixture is stirred for 14 hours and then added to 100 ml of distilled water. After cooling the reaction medium to 0° C., the mixture is filtered and the white solid obtained is dried under vacuum to yield 7.4 g (98%) of pregnenolone tosylate.

The 7.4 g of pregnenolone tosylate is refluxed with methanol (50 ml) for 4 hours. After cooling and evaporation of the solvent, the crude reaction product is taken up in 100 ml of ethyl and washed 3 times with 100 ml of a 10% sodium bicarbonate solution. After drying the organic phase over Na₂SO₄, it is evaporated dry under reduced pressure to yield 5.2 g (100%) of 3-methoxy-PREG in the form of a white powder.

A novel synthesis of 3-methoxy-PREG was performed on a kilogram scale. The purity of the end product was confirmed by NMR and was greater than 97.5%, with only one minor contaminant easily separable by HPLC. Pregnenolone can be obtained at low cost from commercial sources.

Example 2 Test of 3-methoxy-PREG (43B) Activity; Comparison with Pregnenolone (PREG)

This in vitro test measures the effect of molecules on the MAP2-induced polymerization of microtubules. This polymerization occurs when MAP2 proteins and tubulin are mixed at adequate concentrations in the presence of GTP. It is accompanied by an increase in optical density measured at 345 nm for 15 to 30 minutes with a UNICON spectrophotometer thermostated at 37° C. (FIG. 1).

It is observed that molecule 43B, corresponding to 3-methoxy-PREG, activates microtubule polymerization as does pregnenolone (PREG). Other molecules, such as progesterone and pregnenolone sulfate, are PREG antagonists and do not stimulate polymerization (not shown).

Example 3 Cellular Models Effect of Molecules on Neuritic Growth

To test the effect of selected molecules on neuritic growth, we first used the PC12 line, which has long been employed in neurobiological research. In the presence of NGF (nerve growth factor), the cells of this line, which arise from a rat pheochromocytoma, form neuritic extensions containing MAP-associated microtubules. The growth of these elongations is stimulated by the addition of PREG. In the presence of PREG (30 μM), the increase in the average length of the neurites after 3 days of culture reaches 60%. The screening of other natural or synthetic steroids made it possible to select several molecules presenting greater effects than that of PREG (FIG. 2). In particular, the addition of molecule 43B, which can be synthesized easily from PREG, caused a spectacular increase (reaching as high as 500%) in the length of neurites formed in the presence of NGF (FIG. 3). This neurite growth accompanies the stimulation by 43-B of the association of MAP2 to the microtubules (FIG. 4).

Effect of Steroids on the Resistance of Microtubules to Nocodazole

Nocodazole is a microtubule depolymerizing agent. Its addition to PC12 cell cultures, differentiated in the presence of NGF, causes neurites to retract as a result of the depolymerization of their microtubules. Pretreatment of the cells by PREG or 43B makes the neurites resistant to nocodazole due to an increase in the stability of their microtubules, a condition necessary for the formation of long neurites (FIG. 5).

Effect of Steroids on the Cytotoxicity of Okadaic Acid

Okadaic acid is a protein phosphatase inhibiter. Thus, the hyperphosphorylation of tau protein is implicated in microtubule depolymerization and in human neuroblastoma HS-SY5Y cell death. The exposure of SY5Y cell cultures to okadaic acid does in fact cause significant cell death. Cell death is decreased by the simultaneous addition of PREG and the same effect, only much stronger, is seen by the simultaneous addition of 3-methoxy-PREG (43B) (FIG. 6).

Example 4 Tests of Toxicity Cellular Toxicity

Cellular toxicity tests are carried out routinely on the PC12 cell line. The initial results show that PREG and 43B do not demonstrate toxicity at concentrations as high as their solubility limits (approximately 50 μM).

In Vivo Toxicity

In rats, the daily injection for one month of 48 mg/kg of 43B (which is 4 times the active dose for medullary trauma) affected neither average weight nor behavior.

Example 5 In Vivo Experiments—Medullary (Spinal Cord) Trauma Medullary Contusion Model

To determine the neuroprotective effects of the molecules tested, a medullary compression model is used. This model involves the total paralysis of the animals in the first few days following the operation. This period of paralysis is followed of a phase of approximately three weeks during which the animals partially recover their motor function. The study of this recovery using a simple and precise functional test based on observation of the animals (the BBB score) makes it possible to study the speed and the degree of recovery of the animals, with and without treatment.

Two groups of rats were subjected to medullary compression. Then, daily for 2 weeks, the animals received a subcutaneous injection containing either sesame oil alone (control group, n=20), or sesame oil containing molecule 43B (43B group, n=20; 12 mg/kg/day). The first injection was given 5 minutes after medullary compression. Locomotion of the animals, using BBB scores, was evaluated in a blind format on post-operation days 1, 4, 7, 14, 21, and 28. Three animals in each group had to be excluded from the study. Statistical analysis of the results using the nonparametric Mann-Whitney test shows that the animals treated with 43B present results quite significantly higher than the control animals as of post-operation day 7 (FIG. 7).

Example 6 In Vivo Experiments—Cerebral Ischemia

Two models of cerebral ischemia in the rat were developed.

The first is a permanent or transient focal ischemia model of the middle cerebral artery using electrocoagulation or clamping (evaluation of neuroprotection by quantification of the volume of the lesioned area).

The second is a transient global cerebral ischemia model. This model is created in the rat by electrocoagulating and severing the vertebral arteries and then clamping the carotid arteries for a period of 15 minutes (evaluation of neuroprotection and cerebral plasticity increase by quantification of neuronal loss in the CA1 region of the hippocampus and by memory tests).

Example 7 In Vivo Experiments—Alzheimer-Type Neurodegenerative Disease Model (Transgenic Mice)

In order to evaluate the therapeutic potential of 43B to treat Alzheimer-type neurodegenerative diseases, a homozygous transgenic line of mice, such as described by Götz (EMBO J. 1995; 14(7):1304-13), can be used.

These mice express the longest human tau protein isoform. They present symptoms of neurological dysfunction expressed as muscular weakness and a reduction in motor coordination which correlate histologically with the appearance of abnormal neurites and hyperphosphorylated tau proteins as is seen in Alzheimer's disease. This pathological phosphorylation decreases the affinity of tau for microtubules and favors its aggregation.

By treating these mice with molecules that increase microtubule stability, it is intended that the proportion of tau protein associated with the microtubules is increased and thus the appearance of symptoms is delayed.

A breeding program was undertaken at Bicêtre and genotyping made it possible to select mice homozygous for the transgene. At the age of 21±3 days, 3 groups of 10 mice were assembled and each group then received subcutaneously either an empty implant, an implant of PREG, or an implant of 3-methoxy-PREG. These implants released 0.38 mg of steroid per day for 90 days. The progression of motor incoordination was followed by repeated RotaRod tests. Only the 3-methoxy-PREG had a beneficial effect on motor dysfunction (FIG. 8).

Example 8 In Vivo Experiments—Mnemonic Performance Mnemonic Deficit Induced by Colchicine

Colchicine, a substance which depolymerizes microtubules without blocking protein synthesis, is injected at very low doses that do not induce neuronal death in the rat hippocampus. These injections cause a learning deficit which results from lasting microtubule depolymerization. The objective is to test the effect of microtubule-stabilizing molecules on mnemonic deficits and histological lesions in the hippocampus induced by colchicine.

Mnemonic Deficit During Ageing

Studies on ageing are carried out on old rats presenting mnemonic deficits. The objective of this experiment is to mitigate these deficits by a chronic treatment with our molecules.

The two-step memory experiments are based on the spontaneous exploration of novelty and are adapted from the experiments described by Dellu et al. (1992, Brain Res., 588, 132-9) and Ladurelle et al. (2000, Brain Res., 858, 371-9). The technical instructions from these two publications concerning spatial memory tests using labyrinths are included in reference to the present application.

Example 9 Pharmacokinetics

The pharmacokinetics of the molecules tested in vivo are evaluated using gas chromatography/mass spectrometry (GC/MS) assays.

A study was conducted with PREG and molecule 43B. Its primary objective was to show that molecule 43B crossed the blood-brain barrier.

Rats were injected with either PREG or 43B diluted in sesame oil and assayed by GC/MS for the quantity of PREG or 43B in various organs at 1, 4, 8, and 24 hours after injection (12 mg/kg in 0.5 ml of sesame oil; subcutaneous injection).

The results presented in FIG. 9 show that molecule 43B penetrates rapidly into the spinal cord and the brain of the injected rats, and tends to accumulate there.

These results obtained in vitro and in vivo clearly demonstrate that molecule 43B (3-methoxy-PREG) gives spectacular results on the growth of neurites in culture and on the medullary compression model.

Example 10 Other Molecules According to the Invention

The indices of binding and activity are expressed as a percent of PREG.

Binding (affinity) is measured by the displacement of PREG-³H.

Activity is measured by the increase in optical density at 345 nm of a mixture of purified tubulin and MAP2, incubated at 37° C. in the presence of GTP.

Stimulation of neuritic sprouting is conducted on PC12 cells differentiated in the presence of NGF (10 ng/ml) and the steroid being tested (30 μM) for 3 days. For each condition, the average length of the longest 200 neurites in each cell is measured simultaneously for 3 cultures.

The results are represented by one, two or three crosses (+) according to whether stimulation is lower than, equal to, or higher than that produced by PREG.

Neuritic Steroid Affinity Activity sprouting Pregnenolone (PREG) 100 100 ++ 3β-methoxy-pregna-5-ene-20- 100 100 +++ one (3-methoxy-PREG) 3β-methoxy-pregna-5-ene-20- 53 113 +++ one-17α-dichloromethyl 3β-methoxy-5α-pregnane-20- 87 10 +++ one 3β-methoxy-5α-pregnane-20β- 65 65 ++ ol PREG-16α-methyl 80 70 ++ PREG-16β-methyl 63 67 (++) 3β-methoxy-pregna-5,14- 102 50 + diene-20-one PREG-16α,17α-epoxy 41 54 + PREG-16α,17α-methylene 62 49 + Pregna-5-ene-3β,20β-diol- 60 108 ++ 20-acetate 3β-hydroxy-5α-pregnane-20- 57 53 (+) one-16α-methyl

These results show the effectiveness of other molecules derived from pregnenolone to stimulate the polymerization of microtubules induced by MAP2 and to stimulate neuritic sprouting. For those that are not 3β-methyl derivatives, it is foreseeable that these derivatives will at least maintain their activity.

Example 11 Activity of 3-methoxy-pregnenolone on Progesterone Receptor

The capacity of 3-methoxy-pregnenolone to display progesterone activity, and thus to be considered as a progestin, was tested by assaying the activity of 3-methoxy-pregnenolone on progesterone receptor.

Indeed, progesterone is an agonist of progesterone receptor, as are all progestins. In contrast, compounds able to inhibit progesterone activity on its receptor are called progesterone receptor antagonists.

Methods

The main experimental setting used is the following: HEK293T cells were transiently transfected, using calcium phosphate precipitation technology, with expression vectors pSG5hPR (which permits expression of human progesterone receptor (PR)), pFC31-luc (contains the luciferase gene under the control of the MMTV promoter, which is in turn activated by binding of a progestin to progesterone receptor) and pcbetagal (which permits expression of betagalactosidase), and cultured during 24 hours with increasing amounts of various compositions:

-   -   1. Test of progesterone receptor agonist activity: transfected         cells were cultured with increasing amounts of progesterone or         3-methoxy-pregnenolone     -   With this setting, a compound with progesterone receptor agonist         activity permits a transactivation activity resulting in the         expression of luciferase (since the binding of a progestin to PR         results in activation of the MMTV promoter, which directs the         expression of luciferase).     -   In contrast, a compound without progesterone receptor agonist         activity does not permit a transactivation activity and         luciferase is not expressed (since PR is not activated and thus         does not activate the MMTV promoter);     -   2. Test of progesterone receptor agonist activity: transfected         cells were cultured with progesterone (1 nM) and increasing         amounts of RU486 (a well-known progesterone receptor antagonist)         or 3-methoxy-pregnenolone.     -   With this setting, a compound with progesterone receptor         antagonist activity competes with progesterone for the         occupation of progesterone receptor and results in a progressive         loss of transactivation activity when the amount of this         compound is increased compared to progesterone.

Results

The results obtained with experimental setting 1 (test of progesterone receptor agonist activity) are displayed in FIG. 10.

FIG. 10 clearly shows that, contrary to progesterone, which permits a transactivation activity leading to the expression of luciferase, 3-methoxy-pregnenolone does not permit such a transactivation activity, even at the highest tested concentrations, thus demonstrating that 3-methoxy-pregnenolone does not have progesterone receptor agonist activity, and cannot thus be considered as a progestin.

The results obtained with experimental setting 2 (test of progesterone receptor antagonist activity) are displayed in FIG. 11.

These results unambiguously show that even if 3-methoxy-pregnenolone does not have the very high antagonist activity of RU486, it is a weak progesterone receptor antagonist.

Example 12 In Vivo Experiments-Treatment of Depression Microtubule Dynamics

Acute Effects of Pregnenolone (PREG) and 3-methoxy-PREG (43B) Administration on Microtubule Dynamics in Rat Hippocampus.

Adult male (250-300 g) Sprague Dawley rats received a single injection of pregnenolone (PREG) and 3-methoxy-PREG (43B). The effects produced by neurosteroids were compared with those produced by acute administration of the antidepressant drug fluoxetine (selective serotonin reuptake inhibitor; SSRI). A single administration of PREG (10 mg/kg subcutaneously) or 3-methoxy-PREG (10 mg/kg subcutaneously) significantly increased the ratio between the dynamic tyrosinated α-tubulin and the stable detyrosinated α-tubulin (Tyr/Glu-Tub ratio) in rat hippocampus 3 h following injection (FIG. 12A). Additionally, the stable acetylated α-tubulin (Acet-Tub) was significantly decreased by both PREG and 43B (FIG. 12B). These findings suggest increased microtubule dynamics, and function and indicate a potential acute promoting effect of 43B on hippocampal structural neuronal plasticity. In contrast, acute fluoxetine did not change Tyr/Glu-Tub ratio (FIG. 12A) and showed a tendency to increase Acet-Tub (FIG. 12B). These data are in line with previous reports showing a promoting effect of such antidepressant drug only following chronic administration (Warner-Schmidt and Duman, Hippocampus 2006). Therefore, 43B showed the interesting potential to be more effective and quicker than antidepressant drugs in correcting neuronal structural alterations associated with major depression.

Neurosteroids and 3-methoxy-PREG (43B) Levels

Pregnenolone (PREG) and progesterone (PROG) levels in rat plasma and hippocampus 3 h following acute administration of sesame oil (250 μl/rat subcutaneously, n=6) or 43B (10 mg/kg subcutaneously, n=6) are shown in the table below.

Plasma (ng/ml) Hippocampus (ng/g) Treatment PREG PROG PREG PROG Sesame oil 1.15 ± 0.22 0.86 ± 0.23 40.13 ± 13.33 1.37 ± 0.20 43B 1.33 ± 0.34 0.66 ± 0.20 36.22 ± 7.24  1.47 ± 0.16

As expected 43B was not converted back to PREG or metabolized to PROG

Additionally, in the same 43B injected animals, the concentrations of the drug were 21.11±5.04 ng/ml in plasma and 73.3±14.68 ng/g in hippocampus 3 h following injection.

Forced Swimming Test (Fst): Assessing the Antidepressant Activity of 3-methoxy-PREG (43B)

The present experiment investigated the antidepressant effects of pregnenolone (PREG) and 3-methoxy-PREG (43B) compared to those exerted by fluoxetine and desipramine. Adult male (250-300 g) Sprague Dawley rats were randomly assigned to different experimental groups as follow: i) Controls: Water (250 μl/rat subcutaneously, n=6); Sesame Oil (250 μl/rat subcutaneously, n=12); ii) Antidepressants: Fluoxetine (FLX) (10 mg/kg subcutaneously, n=6), Desipramine (DMI) (10 mg/kg subcutaneously, n=6); iii) Neurosteroids: Pregnenolone (PREG) (10 mg/kg subcutaneously, n=14), 3-methoxy-Preg (43B) (10 mg/kg subcutaneously, n=12). Drugs were administered following the traditional dosing regimen used in the FST consisting of three injections: 24, 5, 1 h before testing.

The FST is currently the most widely used animal model for assessing depression related behavior and antidepressant drug activity in rodents (Cryan et al., Neubiorev. 2005). Rats are placed in an inescapable cylinder of water where they develop an immobile posture believed to reflect a “depressive”-like state. The time rats spend immobile is decreased by drugs exerting antidepressant activity.

Additional behaviors can be detected in the FST; namely, climbing and swimming. It has been shown that swimming behavior is sensitive to SSRIs such as fluoxetine whereas climbing is sensitive to norepinephrine re-uptake inhibors (NR1) such as desipramine.

Results showed that 43B significantly decreased rat immobility in the FST, suggesting a potential antidepressant activity of the drug (FIG. 13A).

In addition, both PREG and 43B significantly increased rat swimming in the FST showing a fluoxetine-like profile (FIG. 13B), since rat climbing behavior was not changed (FIG. 13C).

Novel Object Recognition Test (NOR): Assessing Cognitive Effects of 3-methoxy-PREG. (43B)

Cognitive dysfunction, including impaired recognition memory, are common features in depressed patients (Egeland et al., Scand. J. Psychol. 2005). The present experiment explored the ability of 3-methoxy-PREG (43B) administration to increase recognition memory retention in naive animals and to recover recognition memory deficits in animals submitted to the social isolation protocol. Rearing rats in isolation from the time of weaning and throughout adulthood can induce a series of hippocampal structural and molecular deficits paralled by behavioural alterations resembling a depressive-like state (Weiss and Feldon, Psychopharmacology 2001; Bianchi et al., EJN 2006). Recognition memory was assessed using the NOR test which is a two-trial test of recognition memory based on the spontaneous preference of rats for novelty (Ennaceur and Delacour, Behav. Brain. Res. 1988; Bianchi et al., EJN 2006). Briefly, rats are placed in the open field arena for a 3 min period of habituation and then re-placed in their “home” cage for 1 min. The animals are then re-placed in the arena for the familiarization trial (T1) and allowed to explore two identical-objects for 5 min. Following a variable Inter-trial Interval (ITI), rats are then submitted to the choice trial (T2) and exposed to one of the two objects explored during T1 (familiar object) and to a novel object. The ability of the animals to discriminate between the novel and the familiar object is then expressed as: D2-INDEX: [novel object (sec)−familiar object (sec)]/[novel object (sec)+familiar object (sec)] (Ennaceur and Delacour, Behav. Brain. Res. 1988).

Adult male Sprague Dawley rats (350-400 g) discriminated between the familiar and the novel object following 1 min and 1 h ITI (D2-INDEX of 0.48±0.06 and 0.56±0.04, respectively). In contrast, following 4 h of ITI rats showed delay-induced deficits in recognition memory (D2-INDEX of 0.23±0.06).

Test 1: 3-methoxy-PREG (43B) Increased Memory Retention in Naïve Animals.

A constant ITI of 4 h was used. Adult male Sprague Dawley rats (350-400 g) were randomly divided in two experimental groups and received: i) sesame oil (250 μl subcutaneously; n=12) or ii) 43B (10 mg/kg subcutaneously; n=11) immediately after the familiarization trial (T1).

Sesame oil treated rats did not discriminate between the novel and the familiar object following a 4 h ITI. In contrast, 43B (10 mg/kg subcutaneously) treated rats discriminated between the novel and the familiar object showing increased memory retention (FIG. 14A).

The present data clearly show the ability of 3-methoxy-PREG (43B) administration (10 mg/kg subcutaneously) to enhance retention of recognition memory in the NOR test confirming the potential use of 3-methoxy-PREG in the therapy of cognitive symptoms associated with psychiatric and/or neurodegenerative disorders.

Test 2: 3-methoxy-PREG (43B) Induced Recovery of Memory Deficit in Social Isolated Animals.

Male Sprague Dawley rats (post-natal day 25-28) were singly housed (isolated animals, n=14) or housed in groups of 4 per cage (grouped animals, n=14) for 8 weeks. The NOR test was performed using a constant ITI of 1 h: a) Isolated (n=7) and grouped (n=7) rats received one injection of sesame oil (250 μl subcutaneously); b) isolated (n=7) and grouped (n=7) rats received one injection of 3-methoxy-PREG (43B) (10 mg/kg subcutaneously). Injections were made 1 h before animals performed the NOR task.

Control grouped animals (sesame oil injected), as expected, discriminated between the novel and the familiar object following a 1 h ITI, but isolated rats did not (FIG. 14B). However, isolated rats injected with 43B (10 mg/kg subcutaneously) efficiently discriminated between the familiar and the novel object (FIG. 14B).

CONCLUSIONS

A single injection of 3-methoxy-PREG (43B) resulted in an hippocampal concentration of the drug of 73.3±14.68 ng/g of tissue and significantly increased the expression of markers of microtubule dynamics in rat hippocampus. These effects may lead to hippocampal structural neuronal remodeling and formation of new synaptic connections suggesting the potential use of 43B in the therapy of neuropsychiatric disorders characterized by hippocampal structural neuronal alteration and synaptic deficits such as depression. Accordingly, the molecule was tested in an animal model widely used to test the antidepressant properties of novel drugs such as the forced swimming test and showed a clear antidepressant efficacy similar to that of the antidepressant fluoxetine (SSRI). Furthermore, a single injection of 43B can enhance retention of recognition memory in naïve animals and recover recognition memory deficits in animals submitted to social isolation which is a putative animal model of depression. Taken all together, our data strongly indicate that 43B possess antidepressant efficacy accompanied by cognitive enhancing properties. These peculiar characteristics suggest 43B as a promising new pharmacological tool for the treatment of major depression and major depression subtypes such atypical depression, melancholic depression, psychotic depression and geriatric depression. Other subtypes include dysthymia, postpartum depression, post stroke depression, and subcortical ischemic depression. 

1. A method for the treatment and/or the prevention of a depressive disorder, comprising the step of the administration to said patient of an effective quantity of 3-methoxy-PREG or any molecule derived from pregnenolone or from others 3β-hydroxylated steroids/sterols, incapable of being converted into sulfate esters and/or incapable to be converted by oxidation to hormonally active molecules with the aforementioned molecule presenting formula I:

in which:

represents

R1=—CO—; —CH(OH)— or —CH(O—COCH₃)— R2=H or CHCl₂, R3=H or CH₃, or R2 and R3 together form a ring:


2. The method according to claim 1, wherein said depressive disorder is selected from the group consisting of major depression, dysthymia, postpartum depression, post stroke depression, and subcortical ischemic depression.
 3. The method according to claim 2, wherein major depression is selected from the group consisting of atypical depression, melancholic depression, psychotic depression and geriatric depression.
 4. The method according to claim 1, further comprising the administration to said patient of an excipient that makes it possible to formulate the aforementioned molecule derived from pregnenolone to cross the blood-brain barrier.
 5. The method according to claim 1, wherein the administration is by injection.
 6. The method according to claim 1, wherein the administration is oral.
 7. The method according to claim 1, wherein said molecule of formula I is 3β-methoxy-PREG.
 8. The method according to claim 1, wherein said molecule of formula I is 3β-methoxy-pregna-5-ene-20-one-17α-dichloromethyl.
 9. The method according to claim 1, wherein the quantity of 3-methoxy-pregnenolone or of a derived molecule administered to said patient is ranging between 25 and 2500 mg.
 10. A pharmaceutical composition, comprising 3-methoxy-pregnenolone or a molecule derived from pregnenolone that contains a 3-methoxy function of general formula I as an active ingredient, and a pharmaceutically acceptable excipient.
 11. An in vitro method for increasing the stabilization and/or inducing the polymerization of the microtubules in a cell, comprising the step of exposing the aforementioned cell to the presence of 3-methoxy-pregnenolone at a concentration of approximately 0.5 to 50 μmol.
 12. An in vitro method for increasing neuritic sprouting in a cell, comprising the step of exposing the aforementioned cell to the presence of 3-methoxy-pregnenolone at a concentration of approximately 0.5 to 50 μmol. 